Refractory article.



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ATNT airmen.

FRANK J. TONE, OF NIAGARA FALLS, NEW YORK, ASSIGNOR TO THE COMPANY, OF NIAGARA FALLS, NEW YORK, A CORPU;

BORUNDUM TION OF PENNSYLVANIA.

REFRACTORY ARTICLE.

No Drawing.

To all whom it may concern:

Be it known that l, FRANK J. TONE, residing at Niagara Falls, in the county of Niagara and State of New York, have invented a new and useful Improvement in Refractory Articles, of which the following is a full, clear, and exact description.

My invention relates to refractory articles which contain graphite and fused crystalline alumina. Graphite has long been used in the making of refractory articles, especially crucibles for the melting of metals. 1 have discovered that a mixture of graphite, fused crystalline alumina and a suitable binder, such as clay produce a crucible of very superior refractory qualities. Such a mixture as very easy to mold and work in the plastic state, and after burning has a body which is very refractory, less oxidizable than the graphite crucible, of superior strength, and

of high heat conductivity and great dura-' bility.

As a typical mixture which may be employed for the production of articles embodying my invention, 1 take graphite 40 parts;. fused crystalline alumina 40 parts; and plastic clay 20 arts; these proportions being by weight. T e graphite may be natural flake or Ceylon. raphite, or artificial graphite made in the e ectric furnace. It is preferably crushed material of a fineness that will ass through about a No. 16 mesh. The fused crystalline alumina is the well lmown electric furnace product obtained by the fusion of bauxite and sold under the trade names of aloxite, alundum, 'etc.,

which contains from 92 per cent. and upward of alumina; the impurities bein principally oxide of iron, titanium and si lca. I prefer to use a crushed product containing no grits coarser than No. 40, and from this down to the finest owder. The clay is referably a good re ractor grade of p astic clay, properly weathere or aged by mechanical means and analyzing about as follows:

l do not limit myself to this particular clay however, as many clays of varying com- H. a positions will act as satisfactory binders.

Specification of Letters Patent.

oped. In the making Patented Deer ilylbdllfi.

Application filed July 26, 1918. Serial No. 246,872.

proposed. These materials are mixed with water and thoroughly worked in a pug mill until full plasticity of themixture is develof crucibles the well known form of crucible jigger is employed in the molding operation, in which a plaster mold conforming to the outside dimensions of the crucible is revolved on the head of the jigger. A batch of the mixture is put in the mold and an inside forming tool is brought down within the mold and presses the material against the side of the mold at the same time spinning and working the material and forming it to shape against the wallsof the mold as the mold revolves. The

crucibles are then removed from the molds, dried and gfired in kilns in the usual manner.

In the manufacture of graphite crucibles the graphite particles or fiakes have a tendency to aid in forming cleavages or parting planes in the walls of the crucible during the molding operation as the material is worked and spun under the forming tool. The weak spots in 'the structure may not'appear until the crucible isffired; and often not until after it has been in use for some time. T fiud that the addition of the sharp fused crystalline alumina avoids this defect, that the mixture coheres much more strongly, and that there is no tendency for it to form slipping planes along whichpieces of the crucible might spall ofi when put into use. Uri the contrary-there is produced a very strong homogenous structure.

The invention may be applied to many other refractory articles suchas mufies,

torts, bricks, tubes d the like.

The refractory articles produced by my process have many advantages over produced by clayand graphite alone, especially when employed for the melting of metals which absorb carbon. The crucibles made by this process are specially adapted for the melting of iron and steel molten iron or steel has no effect on al y they will withstand sudden changes of temperature very successfully without cracking or spalling. This is a very marked weakness of ordinary graphite crucibles. The heat conductivity of my composition is very high, which means great fuel economy and ease of melting. Fused crystalline alumina is not subject to oxidization as is graphite and the resistance of the composition to oxidization is therefore relatively high. The tensile stren h is greater than that ofordinary grap ite articles and it also resists abraslon very successfully.

I do not limit myself to the sole use of ea ers clay as a binding material, as other materials wil be found of Special value in the specific cases.

I claim: 1. A refractory article containing graphite, fine granular fused crystalline alumina and a binder. 2. A refractory article containing graphite, fine granular fused crystalline alumina, and clay.

In testimony whereof, I have hereunto set my hand.

FRANK J TONE. 

